Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$142.35	11.431%	$158.622	$158.62	$158.60	$158.60
Purchase #2	$81.75	12.341%	$91.8388	$91.84	$91.85	$91.80
Purchase #3	$108.70	7.524%	$116.8786	$116.88	$116.90	$116.90
Purchase #4	$113.57	8.525%	$123.2518	$123.25	$123.25	$123.30
Purchase #5	$46.44	13.817%	$52.8566	$52.86	$52.85	$52.90
Purchase #6	$43.83	13.120%	$49.5805	$49.58	$49.60	$49.60
Purchase #7	$123.66	5.644%	$130.6394	$130.64	$130.65	$130.60
7 purchase totals =	$660.30		$723.6677	$723.67	$723.70	$723.70